1. Field of the Invention
This invention relates generally to a power splitting transmission, and more particularly to such a transmission for high energy and/or for high rotational speeds, in which central sun gears are connected with the shaft of an input drive mechanism and an output driven mechanism and are coupled with one another by means of two sets of at least three double power splitting gears each, where the at least three double power splitting gears in each set are arranged equidistantly about the circumference of their respective sun gears, and where the double power splitting gears in one set are connected to corresponding double power splitting gears in the other set by membrane couplings.
2. Description of the Prior Art
The tendency toward increasingly high energy and rotational speeds in engines and processing machines requires new types of construction for toothed wheel gearings in order to be able to meet such increased demands.
The difficulties which arise from such increased demands result primarily from the high rotational speeds and the size of such types of gears. The extent of these dynamic problems is apparent from the extent of the circumferential speeds which occur within the toothing units. This can be greater than 200 meters per second and, in other components, can sometimes be up to 300 meters per second.
A two-stage power splitting transmission with coaxial drive starting and stopping shafts, two sun gears and a stationary frame, is known in the art from German patent DE-AS 1 149 958. In this construction, attempt is made to compensate for manufacturing and toothing defects and thereby provide for uniform power distribution, by connecting the individual gears of the power splitting transmission with one another in a rotationally rigid manner by coupling teeth, whereby one double power splitting gear is axially conducted and the individual gears of the other double power splitting gears are axially movable. Additionally, separately manufactured coupling rings are provided, which, after being used to adjust the static tooth profile, are screwed and pegged to the individual gears. This type of construction requires a complicated overall mounting. It is necessary to initially mount both gear sets temporarily, to set the toothed gears into profile engagement, and then to subsequently detach the gear sets again so as to attach the coupling rings to the individual gears when they are returned to their initial position.
Despite such complicated measures, complete compensation for defects can not be achieved when rotating the toothed gears, because the defects occur irregularly about the circumference of the gears and also are of different magnitudes. Because of the wide range of tooth positions which occur, even gear meshing is not possible with this known type of transmission.
Furthermore, such construction requires making the double helical gearing axially self-adjusting because the teeth of the gear coupling are stressed by torque and are displaced axially against one another. In order to accomplish this, the frictional resistance between the tooth profiles of the gear coupling must be overcome, whereby the level of the frictional resistance is dependent upon the torque and the coefficient of friction which is present. Experience has shown that, in such cases, an increase in the coefficient of friction appears with increasing operating times. A greatly increased coefficient of friction can ultimately lead to blocking of the coupling.
An additional disadvantage is that the double helical gearings are, apart from the torque forces, additionally stressed by the friction resistance. The result is that the additional stress has to be considered in the design of the gear set, which leads in turn to an increase in the size of such types of transmissions.
Furthermore, the unsatisfactory articulation of a simple gear coupling does not allow the individual gears to be adjusted, without reciprocally influencing each other, to uniform profile support along the width of the tooth. This task is made more difficult by the fact that the tangential gear forces acting on both the individual gears are directed in opposite directions. This results in a displacement of the individual gears, likewise directed in opposite directions, within the framework of the same, which the bearing clearances provided permit. This displacement necessarily leads, in the positioning of only one simple gear coupling as a connecting element between the power splitting gears, to an obliquely inclined positioning of these gears, and thereby to a support of the profiles which is damaging to one side.
It is, furthermore, a great disadvantage in the positioning of gear couplings as a connecting element in the component groups of the sun gears and power splitting gears, that these component groups cannot be counterbalanced in the mounted condition. The main causes for this are the clearances present during stoppage and during rotation. Among these clearances are the profile clearance, the centering clearance, and the enlargement of these clearances through the greater enlargement of the outer, larger part relative to the inner, smaller part. This disadvantage is particularly great at very high rotational speeds. The unbalancing forces which thereby arise can then easily reach levels which become a serious danger for the transmission, but also for the entire set of machinery, such as, for example, abrasion and corrosion of the teeth, damage to the supports, and breakage of the shaft.
During the use of double power splitting gears, the rotationally rigid connection of the individual gears by means of gear coupling also leads to the disadvantage that, despite the self-adjustment of the sun gears, a power splitting to more than three branching lines is, because of the lack of elasticity, not possible and larger transmissions therefore once again result.
Another construction is shown in German patent DE-PS 1 650 857 which discloses a multiple path transmission for large energy applications. Said construction provides the solution to the problem, in the case of double power splitting transmissions, of compensating the displacement of the individual gears directed by the gear forces in an opposing direction. Furthermore, the influence of the unavoidable defects in production and toothing during the operation should be further reduced and, specifically so, with the smallest possible expenditure in space and construction. A simple helical gearing with a pressure cog is provided as the toothing.
This construction proposes to attain compensation for defects during the operation through the rotational elasticity of the slotted coupling sleeve. In order to be able to mount a transmission constructed in this manner, it is necessary, during the production of the toothing units, that the position of the operating toothing units to the coupling toothing units be precisely equal in all of the power splitting lines. This requirement can, however, only be fulfilled by precise manufacturing means at great expense.
It is one additional constructional characteristic of this construction that the axial guidance of the gear sets with the sun gears is carried out in a rigid manner by means of stopping rings. Additional undesirable stresses result on the toothing units with this construction. Furthermore, this transmission partly entails, through the use of gear couplings with the sun gears and double power splitting transmissions, the same disadvantages as in the construction shown in German patent DE-AS 1 149 958. These are the following: frictional resistances in the gear couplings during axial movements, and thereby additional stresses on the toothing units and pressure cogs, as well as additional dynamic overloads through reduced balancing quality as the result of the complete balancing of the components of the sun gears and the double power splitting transmissions.
Another spur gear/planetary transmission with a self-activated compensation of gear pressure is known from German patent DE-AS 1 173 305. This construction involves pure planetary gearings of the one- and two-stage construction type. In accordance with the patent, a spur gear/planetary transmission is to be created, which can be built in a less expensive manner, as well as lighter and cheaper. Such a construction is not suitable for higher energy and rotational speeds. The types of couplings which are used represent an additional impediment for attaining higher energy and rotational speeds in the known constructions. All of these types of constructions are suitable only for slow or average rotational speeds. For example, in spring/plate couplings, circumferential speeds of approximately 40 meters per second are the maximum values which are presently attainable.
For the solution of the task stated above, there is additionally proposed a two-stage planetary gearing, in which the planet support of the first stage is connected with the sun gear of the second stage by means of a screw spring coupling or bending deflector, an axially rigid shaft, or a rotationally-rigid spring-plate coupling.
A toothed wheel gearing with subdivided gears is also known from German patent DE-PS 370 961. In this patent, the task consisted of achieving, in the case of herringbone gears, a uniform, precise application and support of the teeth of both halves of the portion of the herringbone part with one another. The halves of the herringbone parts are, for this purpose, guided into two supports and connected by means of a single-pivot membrane coupling, without an axial displacement or rotation of the parts against one another being possible. Furthermore, the coupling should permit an oblique placement of the axes of the gearing parts.
An additional known structure is shown in German patent DE-PS 3 622 671 which shows a thrust plate arrangement, particularly for planetary gears within a planetary support. This consists of thrust plates positioned internally and externally, which are provided with recesses for supplying lubricating oil to the support apparatus. There should be attained by this means, even at high rotational speeds of the planetary gears, an absolutely reliable lubrication and cooling of the needle units of a needle supporting apparatus rotating at half rotational speed.